可溶性

Each student pair requires a ring stand, burette clamp, 50-mL glass burette, thermometer clamp, digital and glass thermometers, long-stem funnel, volumetric pipette, pipetter, graduated cylinder, five 250-mL Erlenmeyer flasks, two 400-mL beakers, one 150-mL beaker, and a stirring hotplate with stir bar for heating and mixing solutions.

Using a volumetric pipette, transfer 20 mL of concentrated HCl to a 500-mL volumetric flask. Dilute the solution to the 500-mL mark with deionized water and mix on a stir plate until homogeneous. Store the prepared solution in an appropriate bottle until the lab session begins.

Assigning each group a specific temperature—10, 20, 30, 40, or 50 °C—allows students to collect solubility data across a temperature range. This approach enables the class to generate a complete solubility curve showing how borax solubility changes with temperature, providing comprehensive experimental data.

Bromocresol green indicator is prepared as a 0.1% solution in dropper bottles, one per lab group. It serves as a visual indicator to detect the endpoint during titration, changing color when the acid-base reaction reaches completion, allowing students to accurately determine borax concentration.

Place a stock bottle of borax, weighing boats, and a spatula at each weigh station. This setup allows students to accurately measure and transfer the required mass of borax for their assigned temperature. Ensure adequate space and organization so multiple groups can weigh samples simultaneously without cross-contamination.

A volumetric pipette delivers a precise volume of concentrated HCl—exactly 20 mL—ensuring accurate dilution to create a standardized 0.5 M solution. This precision is critical for reproducible experimental results and allows all lab groups to work with identically prepared acid solutions.